The sesquiterpenes with the COVID-19 M inhibitory activity from the L.

The extract of the whole plant of L. yielded four new sesquiterpenes including a novel skeleton (claroguaiane A, ), two guaianolides (claroguaianes B-C, ), and one eudesmanolide (claroeudesmane A, ), together with three known sesquiterpenoids (). The structures of the new compounds were elucidated by spectroscopic analysis especially 1D and 2D NMR spectroscopy and HRESIMS data. Additionally, all the isolated compounds were preliminarily evaluated for the inhibitive activity of COVID-19 M. As a result, compound showed moderate activity with an IC value of 36.81 μM and compound exhibited a potent inhibitory effect with an IC value of 16.58 µM, while other compounds were devoid of noticeable activity (IC > 50 μM).